fix(FunctionBuilder): return type '?void' is now just 'void'

[kakserpom]

A quick fix for these errors:

PHP Deprecated:  Return type of EvenNumbersArray::offsetSet(mixed $offset, mixed $value): ?void should either be compatible with ArrayAccess::offsetSet(mixed $offset, mixed $value): void, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in Unknown on line 0

Deprecated: Return type of EvenNumbersArray::offsetSet(mixed $offset, mixed $value): ?void should either be compatible with ArrayAccess::offsetSet(mixed $offset, mixed $value): void, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in Unknown on line 0
PHP Deprecated:  Return type of EvenNumbersArray::offsetUnset(mixed $offset): ?void should either be compatible with ArrayAccess::offsetUnset(mixed $offset): void, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in Unknown on line 0

Deprecated: Return type of EvenNumbersArray::offsetUnset(mixed $offset): ?void should either be compatible with ArrayAccess::offsetUnset(mixed $offset): void, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in Unknown on line 0

[coveralls]

Pull Request Test Coverage Report for Build 15997940746

Details

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-0.03%) to 20.518%

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Files with Coverage Reduction	New Missed Lines	%
src/zend/_type.rs	1	69.23%

Totals
Change from base Build 15997927037:	-0.03%
Covered Lines:	760
Relevant Lines:	3704

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💛 - Coveralls